A quadrature oscillator that uses LC resonators, each consisting of an inductor (L) and a capacitor (C) connected in parallel, to produce four-phase clocks of different phases by LC resonance is known. Quadrature oscillators are used, for example, in CDR circuits that are used for the high-speed interconnection for sending and receiving high-speed data by wired or wireless communication. CDR circuits recover clocks and data from a data signal in which the clocks are superimposed.
If quadrature oscillators are adjacent to each other, however, the configuration may cause crosstalk between the inductors of the adjacent quadrature oscillators and thus it is difficult to shorten the pitches between the quadrature oscillators. The crosstalk problem may hinder further size reduction in the circuits.
The following is a reference document.
[Document 1] T. Shibasaki, et. al., “4×25. 78 Gb/s Retimer ICs for Optical Links in 0.13 μm SiGe BiCMOS”, ISSCC, 2015.